A review on Hybrid Electric Vehicle and simulation on Hybrid Electric Vehicle Drivetrain Abstract

Simulation methodology

The objective here is to simulate the drivetrain for Electric Hybrid Vehicle (HEV) and study and analyze the different parameters associated with the drivetrain and its components. The simulation of powertrain is done for parallel type of Hybrid Electric Vehicle, in the software called MATLAB Simulink. The Parallel Hybrid Electric Vehicle consists of an ICE, DC-DC convertor, Battery, Electric Motor, transmission and two wheels (Because half- Vehicle model is built, and only rear wheels are included).In the Parallel Electric Hybrid Engine the ICE and Motor output shaft are connected with mechanical coupling or any other linkage mechanism to combine and transfer the power to the transmission.



Figure 1. Parallel Hybrid Electric Vehicle diagram

In the simulation the engine and motor are arranged parallel to each other and unlike the figure 1 above only engine is attached to the transmission and the battery is attached with the DC-DC convertor which supplies electric current to electric motor to drive the shaft and the output shaft of both the transmission and the motor are combined to combine the power produced by both the power sources. Due lack of skills in MATLAB Simulink the control strategy unit was not developed in the powertrain model to command the power source components according to the performance requirements of the vehicle. Therefore, the method used here for knowing the power requirements of the electric motor to drive the wheels was, the engine was kept On at constant throttle to deliver the power to wheels to maintain an initial speed of the vehicle. And the electric motor is used to accelerate the vehicle and maintain a constant speed and then deaccelerate back to the initial speed which means electric motor was switched On during the performance requirement and maintain the performance and then the electric motor is switched Off and the vehicle is cruising with the engine power supplied to the wheels. The Electric motor is managed with the speed command strategy made with help of MATLAB documentation and the electric motor speed is increase and decreased with this strategy. And by changing the electric motor speed the simulation results or the parameters are obtained such as electric power, shaft speed, battery and fuel Consumptions, speed of the vehicle and the battery losses.

The components used here were an engine which was an ideal spark-ignition engine which has simple parameters, and which has max speed of 7000 RPM and max power is 50 KW. And the Gearbox selected here is a simple gearbox with constant efficiency 95%. The electricity is supplied from the battery where it is stored, and it consists of DC voltage source, internal resistance, current and voltage sensor, the DC voltage source is where the electricity is stored and used, the measure of the battery power is done by the voltage and current sensors. And DC-DC convertor is used is an electric-mechanical device which converts the voltage of DC current from high to low or low to high but here during the power conversion, the voltage is increased because the motor requires more voltage current. and the electric motor is used, it was a block set taken from the MATLAB Simulink library sources, basically this converts the electrical energy to the mechanical rotational energy and vice-versa when the engine powers the motor it changes to the generator and charges the battery. The electric motor and the speed command strategy were made with help of the documentation of MATLAB. The electric motor was commanded with inputs in the speed command strategy to accelerate and deaccelerate accordingly at different step timing. The wheel which were used here were also a simple tire which doesn’t have any slip, and which were connected by axle to the main driving shaft coming from the transmission. The Vehicle body dynamics were also measured but assumption was made, the slope of road and the wind speed were not considered and set to zero. the vehicle body was used to measure the normal force acting on the wheels and the speed of the vehicle during different performance.
The Speed command strategy here means to give the command to the electric motor to increase or decrease its speed. So here four inputs are given first is to accelerate motor at a given step time 20s and similarly second input command is given to stop acceleration at 70s to get a constant speed of the vehicle and then the vehicle was deaccelerated by giving input at 120s and giving command to stop acceleration at 170s and then the vehicle was running only on the engine. And these all input signal are combined to one signal by integrating them then they are converted to RPM and it are measured by sensors connected to it for result purpose. And the total duration of the test was 200s and all the parameters such as engine power, battery power, electric power, speed of engine and the electric motor, fuel consumption, etc. were determined by different sensors connected to each component of the simulation.
According to some research, the comparison between the Parallel Hybrid electric vehicle (PHEV) and the conventional ICE Vehicles (ICEV) were made by collecting the data for every parameter in real world driving of both the vehicle type Parallel Hybrid electric vehicle and ICEV and compare them. The Software use here was known as Autonomie. the simulation was done on several driving conditions and many real-life parameters were also measured such as weather conditions, accessories load, road pattern, vehicle activity (driving cycle), and engine capability and also fuel economy, emissions, and all equipment performance were evaluated. The standard driving cycles which were used are FTP, UDDS, and US06HWY. According to results, the fuel economy of Parallel Hybrid electric vehicle was increased up to 68% in real driving condition than the ICEV the reason was due to regenerative braking which was used continuously in city due to which the CO2 and other harmful gas emission decreased up to 40% due using electric mode during less performance required by the vehicle generally in the city traffic. Another benefit was for ECU which can change the power source unit according to required performance, which lead to increase in engine performance by 12% in real world driving cycle whereas in FTP it was 30%.

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